The present invention is related to the spray-drying of nutritional products. More specifically, the invention pertains to the spray-drying of oil-containing nutritional products, especially oil-soluble vitamins. The present invention also pertains to spray-dried nutritional products which comprise gelatin.
The closest related art known to the Applicants is a powder which comprises Vitamin E and gelatin, this powder having been sold by Hoffmann-La Roche, Inc. This product has been sold prior to Jul. 1, 1987. Furthermore, Applicants have analyzed this product known as Vitamin E Acetate 50% SD, and have found that the weight average molecular weight of the gelatin therein is between 15,000 and 25,000, but Applicants have no knowledge of the method Hoffmann-La Roche employs in making this product.
In addition to the vitamin E product sold by Hoffmann-La Roche, a similar product has been sold by Rhone-Poulenc. The Rhone-Poulenc product is comprised of approximately 50 weight percent vitamin E and 50 weight percent gelatin. However, the Rhone-Poulenc product, if resuspended in water, forms an unstable emulsion, and the Rhone-Poulenc powder, if tabletted, forms relatively soft tablets. Furthermore, the gelatin used in the Rhone-Poulenc product has been found to have a weight average molecular weight of 5890, this molecular weight being far below Applicant's claimed molecular weight range.
Also related to the present invention are three U.S. Patents assigned to Hoffmann-La Roche patents being U.S. Pat. Nos. 3,608,083; 3,914,430; and 3,962,384. Each of these patents is discussed briefly below.
U.S. Pat. No. 3,608,083 pertains to a vitamin E powder which comprises a hydrolyzed gelatin. The hydrolyzed gelatin has a "very low Bloom" and "a molecular weight of about 9,000 to about 11,000". The '083 patent fails to state the method by which the 9,000-11,000 gelatin molecular weight was determined. Furthermore, the '083 patent states that very low Bloom hydrolyzed gelatins are advantageous for use in the powder because of their relative heat stability without off-odors developing, while other hydrolyzed gelatins develop unpleasant off-odors when used in granulation and tableting. The '083 patent also states that low Bloom hydrolyzed gelatins are preferable because they impart good tableting characteristics to the composition which comprises these gelatins. The hydrolyzed gelatins of the '083 patent are disclosed as being produced by a controlled hydrolysis of gelatin. In contrast to the '083 patent, the process of the present invention utilizes a partially hydrolyzed gelatin having a weight average molecular weight of about 15,000 to about 35,000 as determined by gel permeation chromatography.
U.S. Pat. No. 3, 914,430 and U.S. Pat. No. 3,962,384 are based on a divisional application and a continuation application, respectively, of an abandoned parent application. While the specifications of the '430 and '384 patents are identical, the '430 patent is directed at a vitamin E powder while the '384 patent is directed at a method of making that powder. Both patents disclose the combination of a hydrolyzed gelatin in combination with a vitamin E oil, the gelatin and oil being spray dried along with other minor excipients. The gelatin described in both '430 and '384 patent is a hydrolyzed gelatin with either 0-Bloom or "low Bloom", the gelatin having a molecular weight of from about 9,000 to 11,000. As with the '083 patent, neither the '430 nor the '384 patents describes how the molecular weight was determined. The examples in these patents describe spray drying both vitamin E and vitamin A as well as a flavor oil, each of these oils being in admixture with a 0 Bloom gelatin during the spray-drying process. Both of these patents describe the gelatin as a hydrolyzed gelatin having a 0 Bloom and a molecular weight range of from 9,000 to 11,000, and both state that the invention is in no way limited to the use of any particular hydrolyzed gelatin.
In contrast to all of the Hoffmann-La Roche patents, the process of the present invention utilizes gelatin having a weight average molecular weight of between about 15,000 and 35,000, as determined by gel permeation chromatography.
The present invention is concerned with the spray drying of an emulsion which comprises an edible oil and gelatin. It has been unexpectedly found that the molecular weight of gelatin is critical to the process of spray drying an emulsion or solution comprising gelatin. If the molecular weight of the gelatin is too high, the gelatin will form a film leading to a skin which prevents the formation of droplets in a normal spray-dry process. The result of this is that the majority of the material exiting the spray-drying nozzle will become plastered on the walls of the spray dryer. The remaining small portion of the material which does not adhere to the walls of the spray dryer is a non-free-flowing, non-particulate, fluffy powder. On the other hand, if the molecular weight of the gelatin is too low, a stable emulsion of the partially hydrolyzed gelatin and edible oil cannot be formed. Furthermore, if the molecular weight of the gelatin is too low, off-odors develop due to the presence of significant amounts of low molecular weight gelatin hydrolysis products. Amine-type off odors are a result of this low molecular weight material. Thus, it has been found that gelatin within a specific molecular weight range is especially suited to making free-flowing edible powders via spray drying without developing any of the problems described above.
U.S. Pat. No. 2,824,207, to Laster, describes a method of spray drying gelatin-containing formulations by having a cooling zone immediately below the spray nozzle. The '207 patent states that the cooling zone is needed in order to permit the formation of droplets. The '207 patent is an alternative to the method of the present invention, and the '207 patent acknowledges the problems (in spray drying gelatin formulations) discussed above. The Applicant of the present invention has discovered a completely different method of avoiding the problems described in the '207 patent.